Specifies the number of journal files for which slots are to
    reserve in the database. The number of slots for journal files
    must be a positive number greater than zero.

    This feature is additive in nature. In other words, the number
    of reserved slots for journal files cannot be decreased once
    the RESERVE clause has been issued. If you reserve 10 slots and
    later reserve 5 slots, you have a total of 15 reserved slots for
    journal files plus 1 slot (totaling 16 reserved slots) because
    you initially get 1 pre-reserved slot.

    You must reserve slots or delete an existing journal file before
    you can add new journal files to the database.

    You cannot reserve journal files for a single-file database.